This invention is directed generally to the tensionless winding and unwinding of flexible material onto and off a reel, and in particular to the controlling of a catenary-like section of traveling web material suspended between a support point and a motor-driven rotating reel collecting or dispensing the material.
U. S. Pat. No. 4,195,791 discloses a method and means for monitoring in a contactless manner the low point of a catenary-like section of a traveling optic fiber in order to regulate a spooling motor rotatably driving a take-up reel. The '791 patent utilizes a video camera positioned alongside the section low point to monitor its rise and fall without physically contacting the material forming the catenary-like section. This feature advantageously permits the tensionless winding of very fragile materials (e.g., glass strands, integrated circuit conductor webs, and the like) onto a take-up reel whose rate of rotation is regulated by the video camera signal output to maintain the low point of the catenary-like section at a predetermined position so as to minimize winding tension (determined only by the weight of material forming the catenary section).
It is an object of the present invention to provide a catenary controller of the contactless type that is more rugged and less costly than the type of controller illustrated by the earlier-noted '791 patent.
It is a further object of the present invention to provide a catenary controller of the contactless type that is adaptable to controlling a wide range of materials having different electrical conductivity characteristics, geometries, dimensions, and compositions.
It is a still further object of the present invention to provide a catenary controller of the contactless type that is suitable for use in an environment when vision-obscuring, airborne dirt and dust would hamper the proper operation of optical catenary controller systems of the type illustrated by the '791 patent.